[CH3:1][C:2]1[C:7]([CH3:8])=[C:6]([N+:9]([O-:11])=[O:10])[CH:5]=[CH:4][N+:3]=1[O-].P(Cl)(Cl)Cl.O.[OH-].[Na+]>C(Cl)Cl>[CH3:1][C:2]1[C:7]([CH3:8])=[C:6]([N+:9]([O-:11])=[O:10])[CH:5]=[CH:4][N:3]=1
2,3-Dimethyl-4-nitropyridin-N-oxide (75.6 g, 0.45 mol) prepared in Step 1 was dissolved in 300 ml of methylene chloride. A solution of phosphorus trichloride (44 ml) in methylene chloride (60 ml) was slowly added to the solution for 30 minutes at −15° C.˜−20° C. The reaction mixture was stirred for 15 minutes at the same temperature and further stirred for 15 minutes at room temperature. The reaction mixture was cooled to −78° C. 50 ml of water was added to the reaction mixture, which was neutralized with a sodium hydroxide solution and then extracted with methylene chloride. The separated organic layer was dried on anhydrous magnesium sulfate and then concentrated under reduced pressure to give the titled compound as a pale yellow solid (65 g, 95%).
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